Planet Earth is 4. 6 billion years old, and that's a long time, basically a third of a lifetime of the universe. And for most of our planet's history, it has been inhabited by microscopic beings.
Life appeared around 3. 7 billion years ago and it has changed the face of our planet. For most of Earth's history, some form of life has been present on the surface, and this allows us to ask a very interesting question.
How far can we go to back in time and still be alive? Or to put it another way, if you were teleported to 100 million years in the past, would you survive? And 500 million?
Or 4 billion of years? So please come with me, because we need to make a quick trip to the past as far as we've managed to stay alive. Just before we go, this video was made in partnership with with Cambly, which is the perfect platform for those who are on the go but don't want to stop studying Do you think you could survive on Earth a billion years from now?
I can't imagine what it would have been like on Earth a billion years ago. And now, back to the video. To begin our journey, we first need to establish some parameters.
What do we need to stay alive? The four great important human needs are a breathable atmosphere, drinking water, macroscopic food in sushi water and a tolerable climate. The current geological epoch in which we live is the so-called Quaternary period, which has already been lasting 2.
5 million years. And its main characteristic is the alternating cycles between ice and heating areas. Modern human beings emerged in this period approximately 270,000 years ago.
We passed through some areas of ice and probably almost extinct for about 100,000 years. So if you were released, near the poles of the Earth 100,000 years ago, you would die for two reasons. Extreme cold or scarcity of resources that comes with the freezing of a good portion of the planet.
But here we have a curious situation. There are records of human beings coping well with climates as well as cold climates. So unless we're talking about very dramatic and punctual things like the extinction of the dinosaurs via space rock, humans are even good at dealing with the climate.
But the problem here is the plural. Humans, with an S at the end. Beings humans as communities are good at surviving in nature.
But a human being alone is vulnerable. And not just because of the climate. Not so long ago, still in the Quaternary era, large animals were much more common.
Tigers, saber teeth, mammoths, giant sloths. And humans can only deal with these challenges in groups. The capacity for social organization is the main factor in our survival.
So to be fair to our species, we need to consider at what times in the past a human community with something around of about 100 people could survive. And this is important because it is precisely with this social organization in groups, literally a community, that it is possible to survive climate variations and the presence of predators and dangerous animals. A group of human beings could survive an ice age.
And the proof is that our ancestors survived. That's why we're here. So we can say that human beings certainly would survive any time during the Quaternary period.
And that's excellent news for you, in case you want to travel to the past. Because just before the Quaternary period, the conditions of habitability on the planet were not so different. Some changes in the landscape, such as the grass that only began to spread in a dominant way about 20 million years ago, in the Neogene period.
And the period before the Neogene marks the recovery of biodiversity after the event that extinguished the dinosaurs. This is the Paleogene period, which began about 65 million years ago, and the greatest danger to human beings in that period would be precisely the consequences of the extinction of the dinosaurs. The asteroid that killed the dinosaurs deposited a lot of dust and soot in the atmosphere, which killed the plants and this caused the collapse of the food chain.
Food became extremely scarce, and the animals large, even those that survived the impact, became extinct as a result. And don't get excited just yet, because human beings here would be part of the group of large animals, even if small when compared to dinosaurs. So for safety's sake, we'd do well to avoid the 1 million years after the extinction of the dinosaurs if we want to survive.
But having said that, and ignoring this dramatic event, it is quite likely that a human community could survive for almost the entire that period between the extinction of the dinosaurs and today. This time window is known as as the Senozoic era, which is the era dominated by mammals and birds. If we go back a little further, we come to what I believe is the funniest moment in this video, living with dinosaurs.
I mean, fun for those who haven't been eaten. That's the Mesozoic era, containing the three periods of the reign of the terrible reptiles, Triassic, Jurassic and Cretaceous. And here a curiosity, the Tyrannosaurus Rex, which is the most famous dinosaur in the movie Jurassic Park, did not live in the Jurassic period, but at the end of the Cretaceous period, 85 million years ago.
And that's an important detail, because dinosaurs ruled the world for hundreds of millions of years, but several different dinosaurs existed at different times during the Mesozoic era. And even having to share the earth with dinosaurs, coexistence would be difficult, but not impossible. The largest predatory dinosaurs could cause a lot of trouble for human communities in the event that both had existed simultaneously, not least because several of them were much larger and more than all the animals that human beings have lived with throughout history.
But there are chances that if the coexistence had happened, dinosaurs wouldn't have been so interested in eating humans for breakfast. Predators outside of situations of hunger and need usually have criteria, avoid eating unknown prey. If that's a good reason not to become friends with a dinosaur.
Keep being unknown. Sharks, for example, don't like to eat humans. When they bite it's either because they thought it was something else or because they're desperate.
Then it wouldn't be so difficult to avoid these predators because they probably wouldn't even go after you. More worrying than dinosaurs would be smaller predators in desperate situations. And this is also a problem that humans of the past have survived.
If we survived living with wolves and lions, and even turned wolves into pugs, we can survive a fast velocity. But shifting our focus a little from discussing predators to other factors of survival, here we can notice some changes in the atmosphere. At the time the earth's atmosphere had more carbon dioxide than today, but still not enough to be toxic to us.
The weather was also warmer, but not by much. The people from Rio de Janeiro would survive just fine. Food existed and was accessible, both in the form of small animals and small mammals that could be hunted and edible plants.
And from the Cretaceous onwards, which starts about 145 million years ago, we can even find fruit. It makes me sad to think that human beings sent for more than 150 million years in the past wouldn't know fruit. So to summarize, it's likely that human beings have been able to inhabit the world since the beginning of the Mesozoic era, 252 million years ago.
That is, of course, ignoring the big white elephant in the room. Or rather, the big rock in the sky, the asteroid in the middle of the road. But I'll confess that neither the dinosaurs expected that.
If we go back even further in time, we enter the Paleozoic era, which began around 542 million years ago. And this era is the era in which complex life forms began to evolve. Long before the Paleozoic era, complex multicellular animals and plants didn't exist.
This means that no food known to humans today would have existed. The first remnants of a world full of large, complex animals and plants like we see today began in the first period of this era, the Cambrian. Even the term Cambrian explosion is sometimes used to describe the rapid expansion in the diversity of fossils found in this period.
Within this diversity we find some complex algae and the evolution of body organization of animals. And the next period, the Ordovician, is the period in which this diversity began to occupy and spread on the surface. If you think of an animal and a plant on the surface, you'll probably think of something that appeared in the Dovician period.
Whether it's the organization of an animal's body or the structure of a plant. That said, not everything from the Paleozoic era is flowers. Actually, nothing is flowers, because flowers were nowhere near evolving yet.
If a human community were transported to the first periods of the Paleozoic era, food would be the real problem. The explosion of animal and plant diversity took place in or near the oceans. This means that human beings traveling to that time in the past would need to keep close to large bodies of water and find ways to fish out the strangest animals they've ever seen in their lives.
But food wouldn't be the worst problem. The atmosphere at the time had oxygen, but there was also a lot of carbon dioxide. And probably the concentrations of were high enough to be toxic.
Depending on the concentration, the presence of carbon dioxide could cause anything from a mild headache, sleep and difficulty concentrating to death. And our best estimates for the atmospheric composition at the time, put carbon dioxide concentrations in the very deadly range. But if luckily the concentrations were low enough to cause the non-deadly effects of carbon dioxide, no one would have much fun then.
Headaches, difficulty thinking, fatigue, all this together with the environmental difficulties could make the period uninhabitable for human beings. In fact, speaking of carbon dioxide, it was precisely during the final periods of the Paleozoic that carbon dioxide was deposited below ground. And this happened when plants and swamps spread on the planet's surface and began to use this gas in their breathing process.
90% of all the coal in the world was deposited in the crust during the Carboniferous and Permian periods, the final two periods of the Paleozoic era. It would probably only be safe to be a human being from the Permian period, 298 million years ago. Humans simply wouldn't have been adapted to live safely before then.
So the planet has been minimally habitable for humans since 298 million years ago, in the Permian period, at the end of the Paleozoic era. If we pushed it a bit and got lucky with the levels of carbon dioxide in the atmosphere, we might even survive a little before then. And with even more luck, perhaps the entire Paleozoic era was habitable, but with a lot of discomfort because of the atmospheric composition.
If you wanted to go further back in time, more than 300 million years, you would need oxygen tanks to survive. And that makes a certain amount of sense. The three eras mentioned, the Paleozoic, the Mesozoic and the Senozoic, together form a geological aeon, which is the Phanerozoic eon, characterized by the explosion in complex life on the planet.
This is the eon of life as we imagine it. The moral of the video is this, the world as we know it, with its complex animals and plants, only began to look the way it does 500 million years ago, from the Cambrian explosion. And that's only 11% of our planet's history.
Before that, the Earth didn't have the capacity to sustain life like ours. So if we wanted to go back in time, we found our limit. Anything past that, and we'd need to deal with scorching temperatures, a toxic atmosphere, meteorite impact hazards or mass extinctions constantly happening around us.
Or perhaps a combination of all of these. And it was in these terrible conditions that life on Earth thrived for most of the time. Remember when I said that life has existed on planet Earth for at least 3.
7 billion years? Complex life with animals and everything else existed for a very small fraction of that time. And that begs the question, who truly are the victors and survivors?
The single-celled life that endured conditions that would kill human beings quickly? Or us, who have anxiety attacks when the internet goes down? I'd love to know what you think in the comments.
Thank you very much and see you next time.
